Photographic stripping paper



F 1 19 0 R. s. BRYCE Em v 2, 25,3

PHOTOGRAPHIC ISTRIPPING PAPER Filed Jan. 7, 1957 AQ'X EMULSION STEARATO CHROM/C CHLORIDE PA P ER 10 Robert 81 Bryce WilIiamIIGrl 8 INVENTOR ATTORNEY a AGENT PHOTOGRAPHIC STRIPPING PAPER Robert S. Bryce and ,William H. Griggs, Rochester, N.Y.,' assignors to Eastman Kodak Company, Rochester,

N.Y., a corporation of New Jersey Application January 7, 1957, SerialNo. 632,697 r Y 2 Claims. c1. 96-83) Thisinvention relates to a photographic dry stripping paper of the type having a gelatino silver halide emulsion layer temporarily adhered to a paper support which support has been treated so as to allow stripping of 'the emulsion layer from it when dry. V

Dry stripping photographic elements have previously been described, for example, in the Nadeau US. Patent No. 2,326,058, granted August 3, 1943, a silverha'lide emulsion is temporarily adhered to a baryta-coated paper stock by means of a layer of a water soluble cellulose ester. The element was intended primarily for use in template Work where the sensitive element is adhered emulsion down onto a metal plate by means of a lacquer, the paper base stripped off dry, the emulsion remaining thereon then exposed and developed followed by cutting or drilling the metal plate as desired in accordance with the silver image developed on the plate. g

The mentioned dry stripping element, while commercially acceptable, has entailed the use of larger quantities of raw materials and more manufacturing operations than are desirable. Also, it has been difi'icult to maintain a product of uniform quality from coating to coating and irregular stripping of the paper base from the emulsion layer has been encountered. Moreover, it has been necessary to cure the metal plates to which .the emulsion has been adhered for excessive periods of time of the order of 18 hours before the mentioned dry stripping operation can be commenced." n

We have discovered that if a paper or similar fiber base such as a photographic paper stock is given a superficial size coating of a Werner complex salt in which a trivalent nuclear-chromium atom is coordinated with a carboxylic acido group having at least '10 carbon atoms, for example, stearato chromic chloride, the resultant sized paper may be coated directly with a gelatino silver halide emulsion which will dry-strip much more readily than when hydrolyzed cellulose ester is used in the stripping layer yet the emulsion adheres sufficiently for normal handling prior to the stripping operation. This utility of the complex chromium compounds is surprising since other materials known to impart hydrophobic properties to fiber surfaces such as cellulose esters, polyvinyl esters, etc. do not provide the requisite surface for adherence of the emulsion. The emulsion may strip readily from such hydro:

phobic surfaces when moist but not when dry. 7

A representative dry stripping paper contemplated by the invention is shown in greatly enlarged cross-sectional view in the accompanying drawing wherein the single figure layer 10 is a paper support, layer 11 the superficial.

size coating of the Werner complex chromium compound and layer 12 the gelatin emulsion layer on the superficially sized paper surface.

The invention will now be illustrated by means a,

detailed example.

2,925,340 Patented Feb. 16, 1960 'ice I 2 Example Practically any paper-sheet issuitable for use in the any convenient manner including spray'coating, air knife or press roll coating or tub-sizing methods well known in the art. When applying a stearato chromic chloride solution by airknife or similar coating methods, an aqueous solution of about 0.5 to 1.0 percent solids is suitable. A

concentration greater than about 1.0 percent tends to impart a somewhat objectionable discoloration to the paper.

,The optimum amount of the Werner complex chromium salt applied to the paper will be found to vary dependingv in part upon the particular salt in use. For example, when methacrylato chromic chloride is used in'place of stearato chromic chloride, approximately 25 to SO'percent more of the salt is required to obtain comparable stripping properties. Y

The paper thus superficially sized with the chromium salt may then be coated with a suitable gelatino silver halide emulsion of moderate hardness.

As mentioned above, the resulting sensitive element may then be laminated emulsion down to the desired base such as a metal plate using a suitable lacquer formula such as a cellulose ester dope to adhere the emulsion to the plate; A very short time thereafter, in some cases after only a few-minute's but preferably after one to two hours, the paper base may, be stripped off leaving the emulsion adhered to the metal plate. The desired photographic operations may then be applied to the emulsioncoated metalplate to obtain animage thereon.

The Werner chromium complex salts useful in the invention as described, include compounds in which a chromium atom is coordinated with a carboxylic acido gro'ups such as, stearato CH3(CHZ)1QCOO palmitato, laurato, methacrylato, abietato, etc. groups. The complex salts may be prepared by reaction of the'appropriate organic acid with chromium compounds by wellknown methods, for example, "as described in the Iler US. Patents Nos. 2,273,040 and 2,359,858. What we claim is:

1. A dry stripping photographic paper comprising a paper support, a superficial coating on-one surface of said support consisting of a Werner complex in which a trivalent nuclear chromium atom is coordinated with a carboxylic acido group having at least 10 carbon atoms,

*anda gelatino silver halide emulsion layerdirectly over said superficial coating. I

2. A dry stripping photographic paper comprising a paper support, a superficial coating on one surface of. said support consisting of stearato chromic-chloride, and a,

gelatino silver halide emulsion layer directly over said superficial coating.

I References Cited in the file of this patent UNITED STATES, PATENTS 2,326,058 Nadeau Aug. 3, 1 943 2,346,755 Hamming Apr. 18,1944 2,392,503 ,Potte'r et al. Jan. 8, 1946 2,648,614

Martin et al. Aug-11, 1953 invention as the emulsion support even an unsized paper r of the waterleaf type. A photographic paper stock may 

1. A DRY STRIPPING PHOTOGRAPHIC PAPER COMPRISING A PAPER SUPPORT, A SUPERFICIAL COATING ON ONE SURFACE OF SAID SUPPORT CONSISTING OF A WERNER COMPLEX IN WHICH A TRIVALENT NUCLEAR CHROMIUM ATOM IS COORDINATED WITH A CARBOXYLIC ACIDO GROUP HAVING AT LEAST 10 CARBON ATOMS, AND A GELATINO SILVER HALIDE EMULSION LAYER DIRECTLY OVER SAID SUPERFICIAL COATING. 